<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script src="https://cdn.bootcss.com/jquery/3.4.1/jquery.js"></script>
    <style>
        .one{
            width:100px;
            height: 100px;
            background: red;
        }
    </style>
</head>
<body>
    <!-- jquery选择器  ajax -->
    <div class="one">

    </div>
    <button class="btn">toggle</button>
    <script>
        var $one = $(".one");
        console.log($one)
        $(".btn").click(function(){
            // $(".one").hide();
            if($('.one').is(":visible")){
                $(".one").hide(300)
            }else{
                $(".one").show(300)
            }
        })
    </script>
</body>
</html>